Aspects of this disclosure are generally related to data storage systems. Data storage systems are used to maintain relatively large data sets and support a relatively large number of concurrent users. The basic building blocks of storage may include storage arrays or storage server clusters. Examples of storage arrays, which will be used herein for the purposes of explanation, include the VMAX family of storage array products of EMC Corporation. Each storage array typically includes multiple physical storage devices which are used by storage directors to present logical volumes of storage. Different types of physical storage devices may be used, and the devices may be organized in hierarchical tiers based on performance. Storage devices may exhibit wear and eventually fail as a function of use. RAID groupings and other techniques may be implemented to decrease the likelihood of data loss and help maintain data availability.